REGIONAL SUMMARY:
During the twenty-first week of 2026, a total of 50 disaster events were reported across the ASEAN region, including floods, landslides, storms, and wind-related disasters in Indonesia, Malaysia, the Philippines, Thailand, and Viet Nam. In Indonesia, Badan Nasional Penanggulangan Bencana (BNPB) reported disaster events across Aceh, Jakarta, West Java, Central Java, East Java, South Kalimantan, Central Kalimantan, East Kalimantan, North Maluku, and Central Sulawesi. In Malaysia, Agensi Pengurusan Bencana Negara (NADMA) reported flooding in Sabah. In the Philippines, National Disaster Risk Reduction and Management Council (NDRRMC) and Department of Social Welfare and Development (DSWD) reported flooding, landslides, storms, and wind-related disasters in Davao, North Cotabato, and Zamboanga City. Meanwhile, in Thailand, Department of Disaster Prevention and Mitigation (DDPM) reported flooding, storms, and wind-related disasters in Nan, Lampang, and Nakhon Ratchasima. Lastly, in Viet Nam, Viet Nam Disaster and Dyke Management Authority (VDDMA) reported storms, winds, flooding, and landslides in An Giang, Lam Dong, Ca Mau, Tuyen Quang, Son La, Phu Tho, Lang Son, Dien Bien, Tthai Nguyen, and Quang Ninh.
HIGHLIGHT:
In Indonesia, flooding affected both Pasuruan Regency and Pasuruan City in East Java Province following heavy rainfall on 19 May. In Pasuruan Regency, intense rainfall in the upstream areas of Pandaan, Purwodadi, and Purwosari increased water discharge in the Kedunglarangan and Welang river basins, resulting in flooding across Purwosari, Bangil, Pandaan, Pohjentrek, and Kraton. Meanwhile, in Pasuruan City, heavy rainfall between 1930H and 2130H UTC+7 overwhelmed drainage systems, causing water overflow and inundation in Gadingrejo, Purworejo, and Panggungrejo. According to BNPB, as of 22 May, these flooding situations affected approximately 3.3K households and impacted around 3.3K houses across both Pasuruan Regency and Pasuruan City. In addition, 13 road access points were disrupted. Relevant authorities are undertaking the necessary response measures to address the situation.
HYDRO-METEO-CLIMATOLOGICAL:
For the past week, data from the ASEAN Specialised Meteorological Centre (ASMC) indicated medium to high seven-day average rainfall across the eleven ASEAN Member States. . During the reporting period, tropical disturbance INVEST 99W over the west Pacific Ocean is forecast to continue developing and move generally north-northwestward over the next few days. Model forecasts suggest that INVEST 99W has a moderate to high probability of tropical cyclone formation during the period of 25–31 May (PAGASA, JTWC).
GEOPHYSICAL:
Seven (7) significant earthquakes (M>5.0) were recorded by Indonesia’s Badan Meteorologi, Klimatologi, dan Geofisika (BMKG), Myanmar’s Department of Meteorology and Hydrology (DMH), the Philippines Institute of Volcanology and Seismology (PHIVOLCS), and Thai Meteorological Department (TMD). Mount Semeru (alert level III) and Ibu (alert level II) in Indonesia, and Taal (alert level 1), Mayon (alert level 3), Bulusan (alert level 1), and Kanlaon (alert level 2) volcanoes in the Philippines reported recent volcanic activity according to Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and PHIVOLCS.
OUTLOOK:
According to the ASEAN Specialised Meteorological Centre (ASMC), for the coming week, wetter conditions are forecast over much of the eastern Maritime Continent, while drier conditions are expected over the western half of the equatorial region. For assessment of extreme, there is a low chance of very heavy rainfall across the ASEAN region. However, there remains a moderate increase in chance of extreme hot conditions over northern Viet Nam, while a small increase in chance of extreme hot conditions is forecast over the northern Philippines and parts of the western Maritime Continent, including eastern Sumatra and the southern Malay Peninsula. A transition to El Nino conditions is predicted in June-July 2026.
Sources:
ASEAN Disaster Monitoring & Response System (DMRS); ASEAN Disaster Information Network (ADINet); ASEAN Specialised Meteorological Centre (ASMC); ASEAN Earthquake Information Centre (AEIC); Joint Typhoon Warning Centre (JTWC);
Indonesia: BNPB, BMKG, PVMBG;
Malaysia: NADMA,
Myanmar: DMH;
Philippines: NDRRMC, PAGASA, DSWD, PHIVOLCS;
Thailand: DDPM, TMD;
Viet Nam: VDDMA;
Various news agencies.
